Our invention relates to a method and apparatus for pulling cable, and particularly for adjusting the maximum tension on lightguide communication cable being pulled through conduit.
Capstan winches have long been used to pull metallic conductor communication cable through underground conduit. More recently, the introduction of lightguide communication cable containing glass fibers has required careful control of the pulling tension. In a system for measuring pulling tension known as a running line dynamometer, a winch line is reeved over a sheave on a load cell. The dynamometer, however, measures only the tension on the winch line itself and not on a cable being pulled by the winch line through conduit. It is also difficult to calculate theoretically the maximum tension on a cable being pulled through conduit primarily because of the vagaries of conduit geometry.
An alternative to avoid the problems of the dynamometer and theoretical calculation is to measure the cable pulling tension directly. A prior in-line cell system has a load cell linked between the winch line and cable. The load cell signal is returned for processing via long conductors in the winch line. The in-line cell system, however, is delicate and inconvenient for routine field use.
It is therefore an object of the invention to provide a new and improved method for adjusting the maximum tension on a cable during installation through conduit. Another object is to provide new and improved apparatus for adjusting the tension on a cable being pulled through conduit.